a) Field of the Invention
The present invention relates to preview brake controlling apparatus and method in which a brake pressure during an automatic control process is set in an automotive vehicle when a front obstacle to be braked is detected.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 7-144588 published on Jun. 6, 1995 exemplifies a first previously proposed collision preventing apparatus for an automotive vehicle in which an automatic brake control is effected so that a collision between a front obstacle and the vehicle is previously prevented from occurring when a distance between the front obstacle and the vehicle does not satisfy a predetermined distance.
A Japanese Patent Application First Publication No. Heisei 6-24302 published on Feb. 1, 1994 exemplifies a second previously proposed automatic preliminary braking system in which a heel detector to detect a heel of a driver""s foot which is rested on a heel rest is used to detect an accelerator manipulation information which is different according to different drivers and before the brake manipulation a preliminary brake pressure is applied.
In each of the first and second previously proposed collision preventing and automatic preliminary brake pressure apparatuses, a lower brake pressure of the automatic (preliminary) brake in a state where the vehicle is approaching to the obstacle gives an effect on a shortage in a free running distance or on an improvement in a responsive characteristic when the driver depresses a brake pedal. However, there is a possibility that the automatic brake control is effected in a case where depending upon an accuracy of an inter-vehicle distance sensor, an object other than the front obstacle on the same traffic lane is and a frequency of manipulating depressions-and-releases on an accelerator pedal. is high. In this case, a deceleration developed due to the effect of the automatic brake control often gives the driver an unpleasant (or uncomfortable) feeling.
On the contrary, it is considered that the set automatic (preliminary) brake pressure may be set to be lower. However, the actually developed vehicular deceleration may be larger than a target value thereof due to a control accuracy of a brake liquid pressure control actuator, a vehicular weight, or a variation in a frictional coefficient of the road surface on which the vehicle is running.
In this case, the application of the automatic (preliminary) brake pressure often gives the driver unpleasant (or uncomfortable) feeling.
It is, therefore, an object to provide preview brake controlling apparatus and method which can provide a preview brake control without giving a vehicular driver unpleasant feeling by activating a preliminary brake pressure during an automatic control process even if a vehicular deceleration equal to or higher than a target value thereof occurs.
According to one aspect of the present invention, there is provided with a preview brake controlling apparatus for an automotive vehicle, comprising: an object detector to detect a relative distance of the vehicle to an object for the vehicle to be braked; an approaching state detector to detect whether the vehicle is approaching to the object on the basis of the relative distance of the vehicle to the object; a vehicular velocity variation rate manipulation situation detector to detect a manipulation situation on a vehicular velocity variation rate; a preliminary brake pressure application start determining section that determines whether the vehicle falls in a preliminary brake pressure application enabled state requiring a preliminary brake pressure application on the basis of detection results by the approaching state detector and by the vehicular velocity variation rate manipulation situation detector; and a brake pressure generator to develop a predetermined minute brake pressure in accordance with a vehicular running condition prior to a vehicular driver""s brake manipulation when the preliminary brake pressure application start determining section determines that the vehicle falls in the preliminary brake pressure application enabled state.
According to another aspect of the present invention, there is provided with a preview brake controlling method for an automotive vehicle, comprising: detecting a relative distance of the vehicle to an object for the vehicle to be braked; detecting whether the vehicle is approaching to the object on the basis of the relative distance of the vehicle to the object; detecting a vehicular velocity variation rate manipulation situation; determining whether the vehicle falls in a preliminary brake pressure application enabled state requiring a preliminary brake pressure application on the basis of detection results at the steps of the approaching state detecting and of the vehicular velocity variation rate manipulation situation; and developing a predetermined constant brake pressure in accordance with a vehicular running condition prior to a vehicular driver""s brake manipulation when determining that the vehicle falls in the brake preliminary application state.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.